A number of programmable sewing machines have been devised and are currently available on the market today, one of which is the Model AMS-206A by Juki. Sewing machines of this type offer a number of advantages. For instance, sewing operations are controlled by computer software. More particularly, sewing patterns stored in computer memory and accessible by the software are used to control the movement of a presser foot assembly which engages and moves the stitchable material relative to the sewing needle to produce a desired, preselected pattern. Consequently, programmable sewing machines are commonly used in commercial, high production applications. One such application is for sewing a selected patterned design around an opening in stitchable material to produce a buttonhole or other desirable design. Although no presently known programmable sewing machine incorporated a punch or other assembly for removing stitchable material prior to that described in U.S. Pat. No. 5,158,026, there are separate punching machines which are commercially available.
Unlike programmable sewing machines, there are non-programmable sewing machines commercially available which integrate a punch assembly with sewing operations. U.S. Pat. No. 345,663 to Blodgett, issued Jul. 20, 1886; U.S. Pat. No. 1,225,247 to Hill, issued May 8, 1917; U.S. Pat. No. 1,650,588 to Allen, issued Nov. 29, 1927; and U.S. Pat. No. 2,515,740 to Smith, et al., issued Jul. 18, 1950 are representative of this type of machine. A number of disadvantages are evident with these types of devices based primarily upon the complex manner in which the drive assemblies for sewing and punching operations are typically coupled and integrated. For instance, maintenance costs for these machines are increased since they are both more difficult to repair and since there are additional parts which are subject to wear and/or breakage. Moreover, the complex integration of both operations effectively limits the use of these machines to one function--that of sewing buttonholes. Relatedly, in order to possibly limit the increase in size necessitated by adding the punching assembly, machines of this type commonly perform punching and sewing operations in the same general area, that being the cylinder bed.
Although welting machines cannot be used for buttonhole sewing operations, such machines do typically perform a material cutting operation outside the cylinder bed. Welting machines are used to form welts for pockets on coats and other articles of clothing. In operation, a downwardly reciprocating knife and a sewing needle which are positioned in close proximity to each other in the cylinder bed are activated with the material appropriately positioned. As the material is advanced, the reciprocating knife cuts the material while the trailing needle sews the welt. Upwardly moving knives positioned outside of the cylinder bed place the two end cuts which define the ends of the pocket. Welting machines, however, are generally limited to a single function due to the manner in which the cutting and sewing operations are integrated. Moreover, although there is a material cutting operation performed outside the cylinder bed, no amount of material is removed since the upwardly reciprocating knife merely separates the fibers forming the material. Furthermore, there is no isolation between components used in the cutting and sewing operations.
One apparatus which addresses the need for a detachable punch-type assembly is U.S. Pat. No. 2,954,001 to Luxenburg, issued Sep. 27, 1960, which generally discloses an automatic eyelet attachment. The eyelet attachment, which includes a punch and presser foot, is positioned on a standard non-programmable sewing machine in place of the original presser foot. When sewing an eyelet, the punch penetrates and spreads fibers but does not actually remove any substantial amount of material. With the punch remaining in the material, the needle stitches a pattern therearound to form the eyelet. A disadvantage of a punch of this type is that the material tends to pucker when the punch is inserted, resulting in a product which may be aesthetically displeasing. Consequently, this puts a realistic limitation on the size of the eyelet that can be produced since larger punches of this type will only increase puckering. Moreover, the punching operation takes place in the sewing area or cylinder bed since the needle actually sews around the punch while in the material to form the eyelet. Furthermore, positioning this eyelet attachment on a programmable sewing machine which automatically advances the stitchable material by movement of the presser foot assembly would not appear to provide an operational system. More particularly, the presser foot assembly of a programmable sewing machine moves during sewing operations which would introduce a problem since the punch disclosed by Luxenburg, which is attached to the presser foot, remains in the material while the eyelet is sewn.
In some applications, it may be desirable to not only remove material portions of stitchable materials with a punching-type assembly, but to dispose of such removed portions as well. For instance, fibers or strands of material may be generated during the removal operations and such materials may collect and adversely affect the performance of the sewing machine. Moreover, in high production applications the removed portions, if not properly disposed of, may also present a number of problems.
A single action pneumatic cylinder punch is available from BIMBA which utilizes one type of a disposal system. The BIMBA cylinder is used to punch relatively heavy materials such as plastics. In this regard, the cutting head is hollow and is connected to a hollow shaft of the cylinder. The cylinder shaft is attached to the piston which has a small orifice therein which is aligned with the hollow portion of the cylinder shaft. Consequently, when air is applied to drive the piston, cylinder shaft, and cutting head in a downward direction, a comparatively small air flow simultaneously passes through the orifice in the piston and through the hollow portion of the shaft and cutting head such that the removed portion, when formed, will be displaced from the hollow cutting head. Therefore, air is actually applied to the portion to be punched prior to the removal of such portion and actually even prior to the cutting head contacting such portion.
In certain applications, the work piece has one or more guide or positioning holes therein to identify the specific location on the workpiece where the hole(s) should be made. In this case, it would be further desirable to also improve upon the accuracy of the placement of the desired hole in relation to its corresponding guide hole.